PREPARATION AND INSPECTION OF MK 20 DEPTH CHARGE PISTOL [Main Title]

A very clear instructional film for RAF armourers, with excellent close up photography. The pistol is a pressure sensitive detonator screwed into a depth charge immediately before it's release into the sea. The film depicts the preparations and inspection routines neccesary to ensure 100 per cent reliability for this critical device.

"Preparations and inspection of the mark XX depth charge pistol": In the preparation hut, remotely located on the station, an armourer removes a pistol from it's wooden storage box, checks the accompanying servicing card, lays the pistol on the bench and prepares to dismantle it. The detonator carrier is removed, followed by other operational components; each item is carefully examined as the narrator explains. Satisfied, the armourer proceeds to partially re-assembled the pistol for the functioning test; the pistol is checked for correct operation using air and not water pressure (of the sea). The pistol is placed inside a pressure vessel which is pressurised to 60 psi (pounds per square inch). the armourer reduces the pressure until the pistol fires at 8 psi., equivalent to a sea water depth of 18 feet. The pistol is set accordingly. This procedure is repeated three times. To ensure the pistol does not fire when it is set to 'safe', the detonator components are removed and the pistol replaced in the pressure vessel; a non-functioning test is carried out, as explained by the narrator. Inspection completed the valve is replaced inside the body of the pistol and the whole unit checked for external rust and corrosion, and replaced in its box plus the updated servicing card. The pistol is returned to the store, ready for immediate use.